RACKING BREAKERS

[bure961]

Can main or distribution circuit breakers be racked on to a live buss in switchgear ? Is there a time the switchgear must be shut down to do the work? Both questions are asked with the though of safe work as 70 e or osha. Thank you

 

[templdl]

Can main or distribution circuit breakers be racked on to a live buss in switchgear ? Is there a time the switchgear must be shut down to do the work? Both questions are asked with the though of safe work as 70 e or osha. Thank you

As long as the breakers are in the OFF position. As a safety precaution there are mechanical interlocks to prevent the breaker from being reached in or out should the breaker be in the closed position.
In addition there are shutters that automatically flip into place over any exposed bus after the breakers are racked out.

 

[copper chopper]

as the post before this one said plus I would be wearing the full 70e suit and helmet when doing this.

 

[Little Bill]

Can main or distribution circuit breakers be racked on to a live buss in switchgear ? Is there a time the switchgear must be shut down to do the work? Both questions are asked with the though of safe work as 70 e or osha. Thank you

Zog, you have a call on line (post) 1! Zog Line 1 please!

 

[zog]

Can main or distribution circuit breakers be racked on to a live buss in switchgear ? Is there a time the switchgear must be shut down to do the work? Both questions are asked with the though of safe work as 70 e or osha. Thank you

Yes they can be racked on to a live bus, however you need to wear the proper PPE. Often times a main breaker will have a very high Incident Energy due to a long clearing time of the OCPD on the HV side of the transformer, if that Ei is >40cal/cm2 it is classified as "Dangerous" and can't be done even with PPE. This is a difficult thing to mitigate so most often you either have to do it on a dead bus or use remote racking devices.

Has your facility done an arc flash study or are you just using the tables?

 

[bure961]

Yes we had a study completed and the main cb is listed using 4 ppe while our distribution breakers are dangerous. All are 480 volts. I assumed we needed to shut down the dangerous breakers but was not sure . Thanks for your help.

 

[zog]

Yes we had a study completed and the main cb is listed using 4 ppe while our distribution breakers are dangerous. All are 480 volts. I assumed we needed to shut down the dangerous breakers but was not sure . Thanks for your help.

In that case I would look into remote racking and remote operators, shutting down a whole lineup can lead to other issues.

 

[Haji]

Yes they can be racked on to a live bus,

With the breaker open.

you need to wear the proper PPE.

With the closed door breaker racking in or out, protection level required may be 0.

 

[zog]

With the breaker open.

With the closed door breaker racking in or out, protection level required may be 0.

Only if it is Arc Ressistant switchgear, which is pretty rare.

 

[Haji]

Only if it is Arc Ressistant switchgear, which is pretty rare.

If the door of the switch gear is opened, its arc resistant property is lost. So the closed door breaker racking is still required.

 

[zog]

If the door of the switch gear is opened, its arc resistant property is lost. So the closed door breaker racking is still required.

Standard metal clad switchgear is not designed nor will it in many cases contain an arc flash. Closed door racking is always prefered but unless the switchgear is arc rated the same PPE requirements exist if the doors are open or closed.